JP2020194025A - Secondary transfer device - Google Patents

Abstract

To provide a secondary transfer device that can be reduced in size, and has a function to temporarily reduce a nip pressure when the leading end and the rear end of a sheet pass through a transfer nip.SOLUTION: A secondary transfer device 30 comprises: a crimping/releasing unit 50 that displaces a secondary transfer roller 41 between a pressing position where the secondary transfer roller sandwiches and presses an intermediate transfer belt 21 with an opposing roller 28, and a separated position where the secondary transfer roller is separated from the intermediate transfer belt; and a high-speed pressure reduction unit 70 that temporarily reduces the nip pressure generated by the secondary transfer roller located at the pressing position when the leading end and the rear end of the sheet pass. The crimping/releasing unit 50 has a crimping cam 54 and a crimping arm 55 that swings in contact with the crimping cam to displace the secondary transfer roller 41 to the pressing position and the separated position. The high-speed pressure reduction unit 70 has a pressure reduction cam 74 and a pressure reduction arm 75 that swings in contact with the pressure reduction cam to displace the secondary transfer roller 41 in a direction in which the nip pressure is reduced. The pressure reduction cam 74 is arranged in a circle having the center at a rotation fulcrum 55b of the crimping art 55 and the radius from the center to the shaft center of the crimping cam 54.SELECTED DRAWING: Figure 2

Description

The present invention relates to a secondary transfer device that secondarily transfers a toner image primaryly transferred on an intermediate transfer belt to paper, and in particular, alleviates an impact when the front and rear ends of the paper pass through the secondary transfer position. Regarding a secondary transfer device that can be used.

In many electrophotographic image forming apparatus, yellow (a toner image of one color component is formed along the outer peripheral surface of an intermediate transfer belt having a predetermined width and an endless ring wound around a plurality of rollers. A configuration is adopted in which image forming units for each color such as Y), magenta (M), cyan (C), and black (K) are arranged. Then, by sequentially superimposing the toner images of each color on the intermediate transfer belt by these image forming units, a full-color color toner image is formed on the intermediate transfer belt, and this is secondarily transferred to the paper. ..

At the secondary transfer position, the intermediate transfer belt is sandwiched between a roller that supports it from the inside and a secondary transfer roller that is urged and pressed by a spring or the like from the outside to form a transfer nip. When the conveyed paper passes through the transfer nip (between the outer peripheral surface of the intermediate transfer belt and the secondary transfer roller), the toner image on the intermediate transfer belt is transferred to the paper.

When the tip of the thick paper enters the transfer nip or the rear end comes out, the load changes significantly, so the orbital speed of the intermediate transfer belt may fluctuate or vibration may occur, causing streaks or unevenness in the image. is there.

To address this issue, the nip pressure is temporarily reduced as the front and rear edges of the paper pass through the transfer nip. For example, in the device disclosed in Patent Document 1 below, a cam is provided on the same axis as the axis of the roller arranged to face the secondary transfer roller with the intermediate transfer belt interposed therebetween, and the convex portion of the cam is formed on the secondary transfer roller. By contacting the contact body provided on the shaft, the distance between the shafts of the secondary transfer roller and the roller facing the secondary transfer roller is widened, and the nip pressure is temporarily reduced.

Further, in the device disclosed in Patent Document 2 below, the driving force of the motor is transmitted to the secondary transfer roller by a transmission mechanism to press the secondary transfer roller toward the intermediate transfer belt and control the torque of the motor. By doing so, the pressure is temporarily reduced. The transmission mechanism of this device consists of a first lever and a second lever that are long in the substantially horizontal direction. One end of the first lever is pivotally supported (fulcrum), and the secondary transfer roller is pivotally supported in the middle (point of action). ), The other end is pivotally supported by a slide hole (the point of action of the second lever) provided at the tip of the second lever. The second lever is pivotally supported with a position slightly closer to the tip than the middle as a fulcrum, and the other end is a force point for receiving the force from the motor.

Specifically, the other end of the second lever extends in a fan shape, and tooth rows that mesh with gears provided on the shaft of the motor are arranged in an arc shape. The first lever and the second lever have a link mechanism, and when the second lever swings according to the rotation angle of the motor shaft, the secondary transfer roller is displaced up and down. A motor is driven to press the secondary transfer roller against the intermediate transfer belt to form a transfer nip. The secondary transfer roller stands still while the force with which the secondary transfer roller is pushed back from the intermediate transfer belt and the torque of the motor are balanced, and the torque of the motor is temporarily weakened when the front and rear edges of the paper pass through the transfer nip. The nip pressure is reduced with.

JP-A-2010-204259 JP-A-2017-83503

In the device disclosed in Patent Document 1, since the cam and its driving unit are provided coaxially with the axis of the roller facing the secondary transfer roller with the intermediate transfer belt sandwiched between them, the device configuration can be configured in the axial length direction of the secondary transfer roller. It gets bigger.

Further, in the apparatus disclosed in Patent Document 2, the action point of the decompression mechanism (second lever) is arranged outside the fulcrum and the action point (position of the secondary transfer roller) of the crimping mechanism (first lever). , The device area in the cross section perpendicular to the axis of the secondary transfer roller becomes large.

The present invention is intended to solve the above problems, and is a secondary transfer device capable of miniaturization while having a function of temporarily reducing the nip pressure when the front and rear ends of the paper pass through the transfer nip. Is intended to provide.

The gist of the present invention for achieving such an object lies in the inventions of the following items.

[1] A secondary transfer device that secondarily transfers a toner image that is wound around a plurality of rollers and orbits on an outer peripheral surface of an intermediate transfer belt having an endless ring and a predetermined width to a paper at a predetermined secondary transfer position. And
The secondary transfer is performed at the pressing position where the intermediate transfer belt is sandwiched and pressed between the opposing rollers abutting on the inner peripheral surface of the intermediate transfer belt and the separation position separated from the outer peripheral surface of the intermediate transfer belt. A crimp release mechanism that displaces the rollers and
The first drive unit that drives the crimp release mechanism and
The nip pressure that the secondary transfer roller in the pressing position presses by sandwiching the intermediate transfer belt between the opposing rollers is applied to the front and rear ends of the paper by the secondary transfer roller and the intermediate transfer belt. A high-speed decompression mechanism that temporarily decompresses when passing between
The second drive unit that drives the high-speed decompression mechanism and
Have,
The crimp release mechanism abuts on a crimp cam supported by a rotating shaft driven by the first drive unit in the same direction as the shaft of the secondary transfer roller and swings in contact with the crimp cam. It has a crimping arm that displaces the secondary transfer roller to the pressing position and the separating position.
The high-speed decompression mechanism swings in contact with a decompression cam supported by a rotating shaft driven by the second drive unit in the same direction as the axis of the secondary transfer roller and abutting the decompression cam. It has a decompression arm that displaces the secondary transfer roller at the pressing position in the direction in which the nip pressure weakens.
A secondary transfer device characterized in that the axial center of the decompression cam is arranged in a circle centered on a fulcrum of the crimping arm and a radius of the axial center of the crimping cam.

In the above invention, since the decompression cam is arranged in a circle centered on the fulcrum of the crimping arm and having a radius up to the crimping cam, the device can be miniaturized. That is, since the high-speed decompression mechanism can be accommodated in the arrangement space of the crimp release mechanism, it is possible to suppress an increase in the occupied space due to the addition of the high-speed decompression mechanism.

[2] The secondary transfer device according to [1], wherein the fulcrum of the crimping arm and the fulcrum of the decompression arm are coaxially located at the same position.

In the above invention, the device can be miniaturized as compared with the case where the fulcrum is separated.

[3] The secondary transfer roller is provided in the secondary transfer unit.
The secondary transfer device according to [1] or [2], wherein the crimp release mechanism and the high-speed decompression mechanism are separated from the secondary transfer unit.

In the above invention, as compared with the case where the member related to the crimp release mechanism and the high-speed decompression mechanism is incorporated in the secondary transfer unit, the configuration of the secondary transfer unit can be avoided from being complicated, and the device configuration can be simplified as a whole. ..

[4] The crimping arm presses the secondary transfer unit via the spring and the decompression arm in this order.
The secondary transfer device according to [3], wherein the high-speed decompression mechanism pushes the spring back to the crimping arm side with the decompression arm to perform the decompression.

In the above invention, if the crimping arm is brought close to the release position to reduce the pressure, it is necessary to displace the crimping arm to the extent that the spring is fully extended. However, if the pressure reducing arm pushes the spring back, the crimping arm is Since the decompression operation can be performed while maintaining the pressing position, the temporary decompression operation can be performed at high speed and smoothly with a stroke with a small number of decompression arms.

[5] When the secondary transfer roller is set to the pressing position by the crimp release mechanism, the pressure reducing cam is displaced to a position where the pressure is reduced and a position where the pressure is not reduced without contacting the secondary transfer unit. The range of motion to obtain is secured,
When the secondary transfer roller is set to the separated position by the crimp release mechanism, the range of motion of the decompression cam is not secured, and the decompression cam does not abut on the secondary transfer unit only at a specific angle position. ,
The secondary transfer apparatus according to [3].

In the above invention, the range of motion of the decompression cam (the space that can be displaced between the decompression position and the non-decompression position) is secured between the secondary transfer unit and the decompression cam at the pressing position in the crimping state, but it is movable at the separation position. The device will be downsized by configuring it so as not to secure the area. That is, if the range of motion is secured even at a separated position where it is not necessary to rotate the decompression cam, an extra space is required to avoid contact between the secondary transfer unit and the decompression cam, but only during crimping, the decompression cam The device will be downsized by ensuring a range of motion and not securing a range of motion when released.

[6] The secondary transfer device according to any one of [3] to [5], wherein the crimp release mechanism and the high-speed decompression mechanism are provided below the secondary transfer unit.

In the above invention, the resist mechanism exists on the upstream side in the paper transport direction of the secondary transfer device, and the fixing portion exists on the downstream side. However, the crimp release mechanism and the high-speed decompression mechanism are provided below the secondary transfer unit. It does not compete with these in terms of space, leading to miniaturization of the device.

[7] The secondary transfer unit has a rotation center and swings,
The secondary transfer device according to any one of [3] to [5], wherein the decompression cam is arranged between the rotation center of the secondary transfer unit and the crimp cam.

In the above invention, the device can be downsized by arranging the pressure reducing cam in the space required for the crimp release mechanism to displace the secondary transfer unit (between the center of rotation of the secondary transfer unit and the crimp cam). Try.

[8] The secondary transfer unit has a rotation center and swings,
2. The second according to any one of [3] to [5], wherein the shaft of the separation roller that separates the paper after the secondary transfer from the intermediate transfer belt also serves as the rotation center of the secondary transfer unit. Next transfer device.

In the above invention, since the position of the separation roller is constant regardless of the swing / displacement of the secondary transfer unit, the paper transfer from the separation roller to the transport path on the downstream side thereof is stable.

[9] From the distance between the center of rotation of the secondary transfer unit and the secondary transfer roller, the distance between the center of rotation of the secondary transfer unit and the location where the secondary transfer unit receives pressing force from the crimp release mechanism. The secondary transfer apparatus according to any one of [3] to [5], which is characterized by a long length.

In the above invention, since the pressing force of the crimp release mechanism is increased by the lever ratio and acts on the secondary transfer unit, the torque required for the crimp release mechanism and the high-speed decompression mechanism is reduced, and the size and cost of the motor and the like are reduced. Can be planned. In the case where the crimp release mechanism uses a spring as in [4], the force of the spring can be weakened according to the lever ratio, and the force required for the high-speed decompression mechanism becomes small.

[10] The secondary transfer device according to any one of [1] to [9], wherein the pressure reducing cam abuts on a rotating body pivotally supported by the pressure reducing arm.

In the above invention, friction can be reduced and the life of the decompression cam can be extended.

[11] The crimping arm and the crimping cam are provided at two locations divided into both ends in the axial direction of the secondary transfer roller, and the high-speed decompression mechanism is arranged inside the crimping arm [1]. The secondary transfer apparatus according to any one of [10].

In the above invention, the size of the secondary transfer device in the axial direction (depth direction) of the secondary transfer roller is reduced as compared with the case where a high-speed decompression mechanism such as a decompression cam is arranged outside the crimp cam.

[12] The decompression arms are provided at two positions divided into both ends in the axial direction of the secondary transfer roller, and the decompression arms are connected to each other by a connecting member.
The decompression cam is arranged at the axial center of the secondary transfer roller.
The secondary transfer device according to [11], wherein the connecting member comes into contact with the pressure reducing cam and the pressure reducing arm swings.

In the above invention, the decompression operation can be performed by synchronizing the decompression arms at both ends.

[13] The decompression arms are provided at two positions divided into both ends in the axial direction of the secondary transfer roller, and the decompression arms are connected to each other by a connecting member.
The decompression cams are arranged near the inside of the crimp cams, respectively.
The secondary transfer device according to [11], wherein the connecting member abuts on each decompression cam and the decompression arm swings.

In the above invention, the influence of bending of the connecting member can be reduced.

[14] A position detecting means for detecting the angular position of the second driving unit and the decompression cam is arranged inside the two crimping cams provided separately at both ends in the axial direction of the secondary transfer roller. The secondary transfer apparatus according to [13].

In the above invention, the size of the secondary transfer device in the axial direction of the secondary transfer roller can be reduced.

[15] The rotating shaft of the crimping cam can be moved in the axial direction when the lock mechanism is released, and the movement releases the engagement between the crimping cam and the abutting member on the crimping arm side.
The secondary transfer apparatus according to any one of [1] to [14].

In the above invention, for example, when the secondary transfer device is stopped in the crimping state due to some trouble, the crimping state is released by releasing the lock mechanism and sliding the rotating shaft in the axial direction, and jam processing or the like. It can be performed.

According to the secondary transfer apparatus according to the present invention, the apparatus can be miniaturized while having a function of temporarily reducing the nip pressure when the front and rear ends of the paper pass through the transfer nip.

It is a figure which shows the mechanical schematic structure of the image forming apparatus including the secondary transfer apparatus which concerns on embodiment of this invention. It is a figure which shows typically the secondary transfer apparatus which formed the nip with the intermediate transfer belt. It is a perspective view which shows the secondary transfer unit. It is a right side view (the view seen from the upstream side in the paper transport direction) which shows the secondary transfer apparatus. It is a figure which shows typically the main part of the secondary transfer apparatus at the time of release. It is a figure which shows typically the main part of the secondary transfer apparatus at the time of crimping. It is a figure which shows typically the main part of the secondary transfer apparatus at the time of decompression. It is a figure explaining the arrangement relation of each part of the secondary transfer apparatus which concerns on embodiment of this invention. It is a right side view which shows the secondary transfer apparatus of the structure which arranged only one decompression cam in the center in the front-back direction. It is a figure which shows the normal state and the state which released the lock mechanism and moved the rotating shaft in comparison.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of an image forming apparatus 10 including a secondary transfer apparatus 30 according to an embodiment of the present invention. The image forming apparatus 10 has a copy function of forming an image obtained by optically reading a document on a recording material such as a recording paper and outputting the image, and a rasterized image based on print data input from the outside on the recording paper. It is a so-called compound machine equipped with a printing function for forming and outputting an image. The recording material is not limited to recording paper, and may be film or cloth. Hereinafter, the recording material will be described as a recording paper.

The image forming apparatus 10 is on a scanner unit 11 that optically reads a document, an operation panel 12 that accepts user operations and displays various information, a control circuit unit 13 that controls the operation of the entire apparatus and performs image processing, and a recording material. An image forming unit 20 for forming an unfixed toner image, a fixing device 15 for fixing an unfixed toner image on a recording paper, a paper feed tray 14 capable of accommodating a large number of recording papers used for image formation, and a paper feed tray. It is configured to include a transport unit 16 and the like for transporting the paper fed from 14.

The image forming unit 20 forms a toner image by an electrophotographic method. The image forming unit 20 forms a toner image of one color component on each of the endless annular intermediate transfer belt 21 having a predetermined width and the outer peripheral surface of the intermediate transfer belt 21 wound around a plurality of rollers (primary transfer). Image forming units 22Y, 22M, 22C, 22K for each color of yellow (Y), magenta (M), cyan (C), and black (K), and a toner image formed on the outer peripheral surface of the intermediate transfer belt. It has a secondary transfer device 30 for secondary transfer to a recording paper. The color-coded image forming units 22Y, 22M, 22C, and 22K are collectively referred to as the image forming unit 22.

The image forming units 22Y, 22M, 22C, and 22K have the same structure as each other, although the colors of the toners used are different. The image forming units 22Y, 22M, 22C, and 22K have a cylindrical photoconductor drum 24 as an electrostatic latent image carrier on which an electrostatic latent image is formed on the surface, and a charging device, a developing device, and the like around the cylindrical photoconductor drum 24. A transfer device, a photoconductor cleaning device, etc. are arranged and provided. Further, it includes a print head 26 composed of a laser diode (LD) which is a laser element, a polygon mirror, various lenses, a mirror, and the like.

In each of the image forming units 22Y, 22M, 22C, and 22K, the photoconductor drum 24 is driven by a drive unit (not shown) and rotates in a fixed direction, and the charging device uniformly charges the photoconductor drum 24 to the print head 26. Scans the photoconductor drum 24 with a laser beam controlled on / off according to a drive signal based on image data of the corresponding color to form an electrostatic latent image on the surface of the photoconductor drum 24.

The developing apparatus performs a developing step of developing an electrostatic latent image on the surface of the photoconductor drum 24 with toner to visualize it. The toner image formed on the surface of the photoconductor drum 24 is transferred (primary transfer) to the intermediate transfer belt 21 at a point where it comes into contact with the intermediate transfer belt 21. The photoconductor cleaning device removes and recovers the toner remaining on the surface of the photoconductor drum 24 after transfer by rubbing with a blade or the like.

The intermediate transfer belt 21 wound around the plurality of rollers is driven by a drive unit (not shown) and orbits in the direction of arrow A in the drawing. In the process of circulation, the toner images formed on the photoconductor drums 24 of the image forming units 22Y, 22M, 22C, and 22K of each color are sequentially transferred onto the intermediate transfer belt 21 and superposed to form a full-color color image ( Toner image) is synthesized on the intermediate transfer belt 21. This toner image is transferred (secondary transfer) from the intermediate transfer belt 21 onto the recording paper by the secondary transfer device 30 arranged at the secondary transfer position D. Further, the toner remaining on the intermediate transfer belt 21 after the secondary transfer is removed from the intermediate transfer belt 21 by the cleaning device 27 provided downstream of the secondary transfer position D.

The fixing device 15 is provided in the middle of the transfer path of the recording paper and downstream of the secondary transfer position D, and the toner image transferred on the surface of the recording paper at the secondary transfer position D is transferred to the recording paper. Pressurize and heat to fix.

The transport unit 16 has a function of transporting the recording paper fed from the paper feed tray 14 to the paper output tray 17 through the secondary transfer position D and the fixing device 15. The transport unit 16 includes transport rollers and guides that form a transport path, as well as a motor that drives the transport rollers. Although not shown, the transport unit 16 has a paper reversing mechanism for double-sided printing that reverses the front and back of the recording paper that has left the fixing device 15 and sends it back to the transport path upstream of the secondary transfer position D. I have.

The control circuit unit 13 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like as main units. Each function as the image forming apparatus 10 is realized by the CPU executing the process according to the program stored in the ROM. The control circuit unit 13 controls the operations of the transport unit 16, the image forming unit 20, the secondary transfer device 30, and the like.

FIG. 2 is a diagram schematically showing a secondary transfer device 30 in which a transfer nip is formed between the intermediate transfer belt and the intermediate transfer belt. The secondary transfer device 30 presses the secondary transfer roller 41 whose axial direction is the width direction (direction orthogonal to the paper surface) of the intermediate transfer belt 21 against the outer peripheral surface of the intermediate transfer belt 21 at the secondary transfer position D. The intermediate transfer belt 21 is sandwiched between the secondary transfer roller 41 and the roller (opposed roller 28) arranged at a position facing the secondary transfer roller 41 among the plurality of rollers around which the intermediate transfer belt 21 is wound, and the transfer nip is inserted. Form.

Hereinafter, the width direction of the intermediate transfer belt 21 (axial direction of the secondary transfer roller 41) is referred to as the "front-back direction". Further, the relative position on the end side in the front-back direction is called "outside", and the relative position on the center side in the front-back direction is called "inside".

The secondary transfer roller 41 is incorporated in the secondary transfer unit 40 that rotatably supports the secondary transfer roller 41. FIG. 3 is a perspective view showing the secondary transfer unit 40. FIG. 4 is a right side view of the secondary transfer device 30 (a view seen from the upstream side in the paper transport direction).

In the secondary transfer device 30, the secondary transfer unit 40, the pressing position where the secondary transfer roller 41 presses against the intermediate transfer belt 21 to form a transfer nip (crimping state), and the secondary transfer roller 41 presses the intermediate transfer belt 21. A crimp release portion (crimp release mechanism) 50 that displaces the secondary transfer unit 40 so as to be displaced to a separated position (release state) away from the crimp release portion 50, and a first drive unit 52 that drives the crimp release portion 50 (see FIG. 4). ) And the nip pressure that the secondary transfer roller 41 in the pressing position sandwiches the intermediate transfer belt 21 between the opposing rollers 28 and presses the nip pressure, and the front and rear ends of the paper are the secondary transfer points D (secondary transfer). It has a high-speed decompression unit (high-speed decompression mechanism) 70 that temporarily depressurizes when passing through the roller 41 and the intermediate transfer belt 21), and a second drive unit 72 (see FIG. 4) that drives the high-speed decompression unit 70. .. The crimp release unit 50 and the high-speed decompression unit 70 are configured separately from the secondary transfer unit 40.

The secondary transfer device 30 has a substantially rectangular flat plate-shaped frame member 34 that is long in the front-back direction (see FIG. 4). The secondary transfer unit 40, the crimp release unit 50, the high-speed decompression unit 70, the first drive unit 52, and the second drive unit 72 are attached to the frame member 34.

As shown in FIG. 3, the secondary transfer unit 40 has a frame member 42 composed of left and right side plates and the like, and the secondary transfer roller 41 is rotatably supported on the frame member 42. A guide plate 43 for guiding the paper to the transfer nip, a separation roller 44 for separating the paper after the secondary transfer from the intermediate transfer belt 21, and the like are attached to the frame member 42. The separation roller 44 is provided at a position separated by a predetermined length from the shaft 41a of the secondary transfer roller 41 to the downstream side in the paper transport direction.

In the secondary transfer unit 40, both ends of the shaft 44a of the separation roller 44 are pivotally supported by a pair of holding plates 34a erected from the vicinity of both ends in the front-back direction of the frame member 34, and the shaft 44a is the center of rotation. (See FIG. 4).

The crimp release portion 50 comes into contact with the crimp cam 54 that rotates in the same direction as the shaft 41a of the secondary transfer roller 41 and is supported by the rotating shaft 53 driven by the first drive portion 52, and the crimp cam 54. It has a crimping arm 55 that displaces the secondary transfer unit 40 to a pressing position (crimping state) and a separating position (released state) by swinging.

A contact roller 55a that comes into contact with the crimp cam 54 is pivotally supported at the tip of the crimp arm 55. The other end of the crimping arm 55 is a rotation fulcrum 55b of the crimping arm 55, and is pivotally supported by a support plate 51 erected on the frame member 34 via a support shaft 51b (see FIG. 4). The crimping arm 55 is oriented so that the contact roller 55a at the tip is on the upstream side in the paper transport direction and the rotation fulcrum 55b at the rear end is on the downstream side in the paper transport direction, and the axial direction of the rotation fulcrum 55b is secondary. It is in the same direction as the shaft 41a of the transfer roller 41. A spring 56 extending spirally upward is attached to a predetermined position between the front end and the rear end of the crimping arm 55.

The high-speed decompression unit 70 includes a rotating shaft 73 that is in the same direction as the shaft 41a of the secondary transfer roller 41 and is driven by the second drive unit 72, a decompression cam 74 that is attached to the rotating shaft 73 and rotates, and decompression. It has a pressure reducing arm 75 that displaces the secondary transfer unit 40 at the pressing position in the direction in which the nip pressure weakens by abutting against the cam 74 and swinging.

A rotating body (connecting shaft, which will be described later) 76 is pivotally supported at the tip of the decompression arm 75, and the rotating body 76 comes into contact with the decompression cam 74. The rear end of the pressure reducing arm 75 is pivotally supported by the support shaft 51b. This portion serves as a rotation fulcrum 75a of the pressure reducing arm 75. The pressure reducing arm 75 is pivotally supported at the same position as the crimping arm 55 also in the axial direction of the support shaft 51b.

The decompression arm 75 has an arm portion 75c extending upward at a predetermined position near the tip end, and a pressing roller 75b that abuts on the secondary transfer unit 40 from below is pivotally supported at the upper end of the arm portion 75c. The upper end of the spring 56 provided on the crimping arm 55 abuts on the decompression arm 75 from below.

In the crimping arm 55, the portion of the contact roller 55a is the force point for receiving the force from the crimping cam 54, the portion pivotally supported by the support shaft 51b is the rotation fulcrum point 55b, and the portion to which the spring 56 is attached is the said. It is an action point for applying an upward force to the pressure reducing arm 75 via the spring 56. In the pressure reducing arm 75, a portion of the rotating body 76 that is pivotally supported is a force point that receives a force from the pressure reducing cam 74 via the rotating body, and a portion that is pivotally supported by the support shaft 51b is a rotation fulcrum point 75a and is a spring. The point of contact at the tip of 56 is the point of action during decompression.

The crimping arm 55 swings around the rotation fulcrum 55b, and when forming the transfer nip, the secondary transfer unit 40 is pressed from below to above via the spring 56 and the pressure reducing arm 75 in this order. In response to this, the secondary transfer unit 40 swings around the shaft 44a, and the secondary transfer roller 41 is pressed against the opposing roller 28. The depressurization is performed by pushing the spring 56 back to the crimping arm 55 side with the depressurizing arm 75.

As shown in FIG. 4, the crimping cam 54, the crimping arm 55, and the pressure reducing arm 75 are provided near both ends of the secondary transfer device 30 in the front-back direction. The two crimp cams 54 arranged separately at both ends in the front-back direction are in phase with each other, and the crimp arms 55 at both ends press the bottom surface of the secondary transfer unit 40 via the spring 56 and the decompression arm 75 in the front-back direction. Press in the same way at both ends of the, and release the pressure.

The rotating body 76 is a columnar connecting shaft 76 for connecting the decompression arms 75 provided at both ends in the front-back direction, and the two decompression arms 75 are interlocked with each other. The decompression cam 74 is provided near the inside of the two decompression arms 75, which are separately provided at both ends in the front-back direction. When the connecting shaft 76 comes into contact with each of the pressure reducing cams 74, the pressure reducing arm 75 swings around the rotation fulcrum 75a. Since the connecting shaft 76 is a rotating body that can rotate (rotate), the contact resistance with the decompression cam 74 is small, and the wear of the decompression cam 74 is reduced.

The second drive unit 72 (motor, etc.) that rotates the rotation shaft 73 of the decompression cam 74 and the position detection sensor 77 that detects the angular position of the decompression cam 74 are two decompression cams that are separately arranged at both ends in the front-back direction. It is located inside the 74.

FIG. 5 is a diagram for explaining the arrangement relationship of each part of the secondary transfer device 30. The fulcrum of the crimping arm 55 (rotating fulcrum 55b) and the fulcrum of the decompression arm 75 (rotating fulcrum 75a) are coaxial and at the same position. The crimping arm 55 is longer than the decompression arm 75. The pressure reducing cam 74 is arranged in a circle centered on the rotation fulcrum 55b of the crimping arm 55 and having a radius from the rotation fulcrum 55b to the axis center of the crimping cam 54. That is, the decompression cam 74 is arranged inside the circle 81 shown by the broken line in FIG.

Further, the pressure reducing cam 74 is arranged between the center of rotation of the secondary transfer unit 40 (the shaft 44a of the separation roller 44) and the crimping cam 54.

From the distance L1 between the rotation center (shaft 44a) of the secondary transfer unit 40 and the shaft of the secondary transfer roller 41, the rotation center (shaft 44a) of the secondary transfer unit 40 and the secondary transfer unit 40 are crimped and released. The distance L2 from the position where the pressing force is received from (the position where the pressing roller 75b provided on the pressure reducing arm 75 abuts on the bottom surface of the secondary transfer unit 40) is lengthened.

Next, the operation of the secondary transfer device 30 will be described.

FIG. 6 shows a state in which the secondary transfer unit 40 is in a separated position (released state). FIG. 7 shows a state in which the secondary transfer unit 40 is in the pressing position (crimping state). FIG. 9 shows a state in which the high-speed decompression unit 70 operates to reduce the nip pressure (decompression state).

In the secondary transfer device 30, when the rotary shaft 53 of the crimp release portion 50 is rotated by the first drive unit 52, the crimp cam 54 attached to the rotary shaft 53 rotates, and the crimp arm 55 is at the tip of the crimp cam 54. When the abutting roller 55a of the above abuts the contact roller 55a, it swings around the rotation fulcrum 55b according to the angular position of the crimping cam 54.

When the secondary transfer unit 40 is displaced from the separated position (release state) to the pressing position (crimping state), the crimping arm 55 rotates a predetermined angle counterclockwise from the position shown in FIG. 6, and the spring 56 and the pressure reducing arm 75 Presses the bottom of the secondary transfer unit 40 toward the opposing roller 28 via this order. FIG. 7 shows a crimping state in which the secondary transfer unit 40 is displaced to the pressing position and the decompression by the high-speed decompression unit 70 does not act.

In the crimping state shown in FIG. 7, the pressure reducing cam 74 is in an angular position so as not to abut on the connecting shaft (rotating body) 76. Therefore, in the crimping state, the pressure reducing arm 75 does not receive a force from the pressure reducing cam 74 via the connecting shaft 76, and is displaced according to the crimping operation of the crimping release portion 50.

When the decompression cam 74 of the high-speed decompression unit 70 is rotated to a predetermined angle position while the crimp cam 54 of the crimp release portion 50 is held at the position shown in FIG. 7, the decompression cam 74 is connected as shown in FIG. The connecting shaft 76 is pushed down in contact with the shaft 76, and the pressure reducing arm 75 rotates slightly clockwise around the rotation fulcrum 75a, and pushes the spring 56 back toward the crimping arm 55 from above.

That is, the pressure reducing arm 75 reduces the nip pressure by blocking the pressing force exerted by the crimping arm 55 on the secondary transfer unit 40 via the spring 56. At this time, the distance between the axes of the opposing roller 28 and the secondary transfer roller 41 is somewhat shorter than the sum of the radius of the opposing roller 28 and the radius of the secondary transfer roller 41 at the time of non-contact, and the nip pressure is two. It is generated by the elasticity of the outer peripheral members of the next transfer roller 41 and the opposing roller 28.

As shown in FIGS. 7 and 8, in the state where the secondary transfer unit 40 is in the pressing position by the crimp release portion 50 (crimping state), the decompression cam 74 does not abut on the secondary transfer unit 40 and is in the decompression position (crimping state). A range of motion that allows rotation is secured between the position shown in FIG. 8 and the position not decompressed (the position shown in FIG. 7). On the other hand, as shown in FIG. 6, in the state where the secondary transfer roller is separated by the crimp release portion 50 (release state), the pressure reducing cam 74 does not abut on the secondary transfer unit 40 because the pressure reducing cam 74 does not contact the secondary transfer unit 40. Only when it is in a specific angle position, the movable range of the decompression cam 74 is not secured.

In the released state, the secondary transfer unit 40 descends downward and approaches the decompression cam 74. Therefore, when trying to secure the range of motion of the decompression cam 74 in this state, the secondary transfer unit 40 and the decompression cam 74 are separated. It becomes necessary to arrange the secondary transfer unit 40 at a position corresponding to the decompression cam 74 and to provide a notch for avoiding contact, which causes an increase in size of the device and difficulty in design.

On the other hand, in the released state, it is not necessary to rotate the decompression cam 74 without a request to switch between depressurization and non-decompression in the first place. Therefore, in the crimping state, the range of motion of the decompression cam 74 is secured so that decompression / non-decompression can be switched, and in the release state, the range of motion of the decompression cam 74 is not secured, and a specific angular position (for example, home) is secured. The device is miniaturized by being configured so as not to come into contact with the secondary transfer unit 40 only at the position).

In the secondary transfer device 30 according to the present invention, the decompression state is temporarily formed by the high-speed decompression unit 70, which is a mechanism different from the crimp release unit 50, so that the decompression / no decompression can be switched at high speed. It can be done at the right time. When the pressure is reduced by displacementing the crimping arm 55 from the crimping state so as to return it to the separated position, it is necessary to displace the crimping arm 55 to the extent that the spring 56 is fully extended. On the other hand, in the secondary transfer device 30 of the present invention, the decompression arm 75 pushes the spring 56 back toward the crimping arm 55 to create a decompression state, so that the crimping arm 55 is maintained at the position at the time of the crimping state. The decompression operation can be performed, and the temporary decompression operation can be performed at high speed and smoothly with a small operation stroke of the decompression arm 75.

The control circuit unit 13 controls the second drive unit 72 of the high-speed decompression unit 70 so that the crimping is temporarily depressurized when the front end and the rear end of the paper pass through the secondary transfer position D. Specifically, a sensor for detecting the front and rear edges of the paper is provided slightly upstream in the paper transport direction at the secondary transfer position D, and the sensor is based on the timing at which the front and rear edges of the paper are detected. The second drive unit 72 controls the angular position of the pressure reducing cam 74 so that the front and rear ends of the paper are in a reduced pressure state for a predetermined period before and after the time when they pass through the secondary transfer position D.

The features of the configuration of the secondary transfer device 30 according to the present embodiment and the effects thereof will be described. As shown in FIG. 5, the secondary transfer device 30 is crimped between the fulcrum (rotary fulcrum 55b) of the crimping arm 55 and the crimping cam 54 (centered on the rotary fulcrum 55b of the crimping arm 55 and crimped from the rotary fulcrum 55b). It is characterized in that the decompression cam 74 is arranged in a circle having a radius up to the center of the axis of the cam 54). As a result, the high-speed decompression section 70 can be accommodated in the arrangement space of the crimp release section 50, and the space increase due to the addition of the high-speed decompression mechanism can be suppressed.

Further, since the fulcrum of the crimping arm 55 (rotating fulcrum 55b) and the fulcrum of the decompression arm 75 (rotating fulcrum 75a) are set to the same position (coaxially and axially the same position), the operating region of the crimping arm 55 and the decompression arm 75 The operating areas of the devices overlap to reduce the size of the device.

Further, the secondary transfer device 30 is characterized in that the crimp release unit 50 and the high-speed decompression unit 70 are provided below the secondary transfer unit 40. As a result, the crimp release unit 50 and the high-speed decompression unit 70 are vacated without competing with the resist mechanism on the upstream side in the paper transport direction and the fixing device 15 on the downstream side in the paper transport direction with respect to the secondary transfer device 30. It can be arranged in a space and contributes to miniaturization of the entire image forming unit 20.

Further, as shown in FIG. 4, the secondary transfer device 30 is provided with a crimping arm 55 and a crimping cam 54 at two locations divided into both ends in the front-back direction, and a high-speed decompression unit 70 (particularly the decompression cam 74) is provided inside these. ) Is placed. As a result, the size of the device in the front-back direction can be reduced as compared with the case where the high-speed decompression unit 70 is provided on the outside of the crimp cam 54.

Further, the secondary transfer device 30 is provided with decompression arms 75 at both ends in the front-back direction corresponding to the crimp arm 55 and the crimp cam 54, and the decompression arms are connected to each other by a connecting shaft 76, and the decompression cam 74 is connected to both ends. It is characterized in that it is provided near the inside of the crimping cam 54 of the above. As a result, each decompression cam 74 can apply a force for decompression to the connecting shaft 76 near the depressurizing arm 75, and the bending of the connecting shaft 76 can be reduced.

As shown in FIG. 9, the decompression cam 74 is configured to be arranged inside the crimping cam 54 provided at both ends in the front-back direction and at the center in the front-back direction. May be good. When the decompression cams 74 are provided at two locations divided in the front-back direction as shown in FIG. 4, there is a possibility that the decompression operation by the two decompression arms 75 at both ends may differ depending on the shape of the cam, the phase shift, and the like. On the other hand, as shown in FIG. 9, in the configuration in which the decompression cam 74 is provided only at one position in the center in the front-back direction, the decompression arms 75 at both ends can be synchronized to perform the decompression operation without being affected by the above difference. it can.

Further, as shown in FIG. 4, the secondary transfer device 30 detects the angular position of the second drive unit 72 and the pressure reducing cam 74 inside the two crimp cams 54 divided into both ends in the front-back direction. It is characterized in that the sensor 77 is arranged. As a result, the size of the secondary transfer device 30 in the front-back direction is reduced. As shown in FIG. 9, even in the case where the decompression cam 74 is one, the second drive unit 72 and the position detection sensor 77 are arranged inside the two crimp cams 54 divided into both ends in the front-back direction. The size of the secondary transfer device 30 in the front-back direction is reduced.

Further, the secondary transfer device 30 is characterized in that the pressure reducing cam 74 is arranged between the rotation center of the secondary transfer unit 40 (the shaft 44a of the separation roller 44) and the crimping cam 54. By this. The decompression cam 74 can be accommodated in the space required for the crimp release unit 50 to displace the secondary transfer unit 40 (between the rotation center of the secondary transfer unit 40 and the crimp cam), and the high-speed decompression unit 70 can be accommodated. The increase in occupied space due to the addition is suppressed.

Further, since the secondary transfer roller 41 is incorporated into the secondary transfer unit 40 to form a unit, miniaturization, improved maintainability, and replaceability of the high-speed decompression unit 70 are improved. Further, since the crimp release unit 50 and the high-speed decompression unit 70 are separated from the secondary transfer unit 40, compared with the case where a part of the members related to the crimp release unit 50 and the high-speed decompression unit 70 is incorporated into the secondary transfer unit 40. Therefore, the complexity of the secondary transfer unit 40 can be avoided, and the secondary transfer device 30 can be simply configured as a whole.

Further, the secondary transfer device 30 is characterized in that the shaft 44a of the separation roller 44 also serves as the rotation center of the secondary transfer unit 40. As a result, the position of the separation roller 44 becomes constant regardless of the swing / displacement of the secondary transfer unit, and the paper is stably delivered from the separation roller 44 to the transport path on the downstream side thereof.

Further, the secondary transfer device 30 is of the secondary transfer unit 40 from the distance L1 (see FIG. 5) between the rotation center of the secondary transfer unit 40 (the shaft 44a of the separation roller 44) and the shaft of the secondary transfer roller 41. It is characterized in that the distance L2 between the center of rotation and the portion where the secondary transfer unit 40 receives a force from the crimp release portion 50 (the contact portion of the pressing roller 75b) is long. As a result, the pressing force of the crimp release portion 50 is increased by the lever ratio and acts on the secondary transfer unit 40, and the torque required for the crimp release portion 50 and the high-speed decompression unit 70 is reduced, resulting in miniaturization and lowering of the motor and the like. Contributes to cost reduction. In particular, in a configuration in which the crimp release portion 50 applies a pressing force to the secondary transfer unit 40 via the spring 56, the spring 56 having a weak repulsive force can be used according to the lever ratio. If the spring 56 having a weak repulsive force is used, the force required for the high-speed decompression unit 70 to push back the spring 56 in the decompression operation is also reduced, and the size and cost of the second drive unit 72 can be reduced.

In addition, in the secondary transfer device 30, the rotating shaft 53 of the crimping cam 54 can be moved in the axial direction by releasing the lock mechanism (not shown), and the movement causes the contact roller on the crimping cam 54 and the crimping arm 55 side. The 55a is misaligned so that these engagements are released. FIG. 10A shows a normal use state locked by the lock mechanism, and FIG. 10B shows a state in which the lock mechanism is released and the rotating shaft 53 is moved in the axial direction to release the above-mentioned engagement. ing. Here, the crimping cam 54 and the contact roller 55a of the crimping arm 55 are displaced from each other and their engagement is released, so that the crimping arm 55 (and the decompression arm 75) is in the released state as shown in FIG. Become.

For example, if the secondary transfer device 30 is stopped in the crimped state or the decompressed state due to some trouble, the lock mechanism can be manually released and the rotating shaft 53 is slightly moved in the axial direction to obtain the crimped state or the decompressed state. Can be released, and jammed paper can be removed smoothly.

Although the embodiment of the present invention has been described above with reference to the drawings, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the range not departing from the gist of the present invention. Is also included in the present invention.

The secondary transfer roller 41 does not have to be incorporated in the secondary transfer unit 40. For example, the crimp release portion 50 may press the shaft of the secondary transfer roller 41 to form a crimp state.

In the embodiment, the crimping arm 55 presses the secondary transfer unit 40 via the spring 56 and the decompression arm 75 during crimping, and the decompression arm 75 pushes back the spring 56 during decompression. 55 presses the secondary transfer unit 40 via the spring 56, and the pressure reducing arm 75 engages with hooks provided at both ends of the secondary transfer unit 40 to slightly displace the secondary transfer unit 40 toward the separation position. It may be configured to reduce the pressure. The shape of the spring 56 is not limited to that illustrated in the embodiment, and may be a leaf spring or the like, and may be an elastic body having necessary elasticity.

In the embodiment, the crimping cam 54, the crimping arm 55, the pressure reducing cam 74, the pressure reducing arm 75 and the like are schematically shown, and the shapes and the like thereof are not limited to those shown in the embodiment. For example, if an arm extending downward is provided at the tip of the decompression arm 75 and the connecting shaft 76 is connected to the lower end of the arm, the position of the decompression cam 74 can be lowered downward to reduce the size.

10 ... Image forming device 11 ... Scanner unit 12 ... Operation panel 13 ... Control circuit unit 14 ... Paper feed tray 15 ... Fixing device 16 ... Transfer unit 20 ... Image forming unit 21 ... Intermediate transfer belt 22, 22C, 22M, 22Y, 22K ... Image forming unit 24 ... Photoreceptor drum 26 ... Print head 27 ... Cleaning device 28 ... Opposing roller 30 ... Secondary transfer device 34 ... Frame member 34a ... Holding plate 40 ... Secondary transfer unit 41 ... Secondary transfer roller 41a ... Second Next transfer roller shaft 42 ... Frame member 43 ... Guide plate 44 ... Separation roller 44a ... Shaft 50 ... Crimping release part (crimp release mechanism)
51 ... Support plate 51b ... Support shaft 52 ... First drive unit 53 ... Rotation shaft 54 ... Crimping cam 55 ... Crimping arm 55a ... Contact roller 55b ... Rotation fulcrum 56 ... Spring 70 ... High-speed decompression unit (high-speed decompression mechanism)
72 ... Second drive unit 73 ... Rotating shaft 74 ... Decompression cam 75 ... Decompression arm 75a ... Rotation fulcrum 75b ... Pressing roller 75c ... Arm 76 ... Connecting shaft (rotating body)
77 ... Position detection sensor D ... Secondary transfer position A ... Circumferential direction of intermediate transfer belt

Claims (15)

A secondary transfer device that secondarily transfers a toner image that is wound around a plurality of rollers and orbits on the outer peripheral surface of an intermediate transfer belt having an endless ring and a predetermined width to paper at a predetermined secondary transfer position. ,
The secondary transfer is performed at the pressing position where the intermediate transfer belt is sandwiched and pressed between the opposing rollers abutting on the inner peripheral surface of the intermediate transfer belt and the separation position separated from the outer peripheral surface of the intermediate transfer belt. A crimp release mechanism that displaces the rollers and
The first drive unit that drives the crimp release mechanism and
The nip pressure that the secondary transfer roller in the pressing position presses by sandwiching the intermediate transfer belt between the opposing rollers is applied to the front and rear ends of the paper by the secondary transfer roller and the intermediate transfer belt. A high-speed decompression mechanism that temporarily decompresses when passing between
The second drive unit that drives the high-speed decompression mechanism and
Have,
The crimp release mechanism abuts on a crimp cam supported by a rotating shaft driven by the first drive unit in the same direction as the shaft of the secondary transfer roller and swings in contact with the crimp cam. It has a crimping arm that displaces the secondary transfer roller to the pressing position and the separating position.
The high-speed decompression mechanism swings in contact with the decompression cam supported by the rotating shaft driven by the second drive unit in the same direction as the axis of the secondary transfer roller, and abuts on the decompression cam. It has a decompression arm that displaces the secondary transfer roller at the pressing position in the direction in which the nip pressure weakens.
A secondary transfer device characterized in that the axial center of the decompression cam is arranged in a circle centered on a fulcrum of the crimping arm and a radius of the axial center of the crimping cam. The secondary transfer device according to claim 1, wherein the fulcrum of the crimping arm and the fulcrum of the decompression arm are coaxially located at the same position. The secondary transfer roller is provided in the secondary transfer unit.
The secondary transfer device according to claim 1 or 2, wherein the crimp release mechanism and the high-speed decompression mechanism are separated from the secondary transfer unit. The crimping arm presses the secondary transfer unit via the spring and the decompression arm in this order.
The secondary transfer device according to claim 3, wherein the high-speed decompression mechanism pushes the spring back to the crimping arm side with the decompression arm to perform the decompression. When the secondary transfer roller is set to the pressing position by the crimp release mechanism, the range of motion in which the decompression cam can be displaced to the depressurizing position and the non-decompressing position without contacting the secondary transfer unit. Is secured,
When the secondary transfer roller is set to the separated position by the crimp release mechanism, the range of motion of the decompression cam is not secured, and the decompression cam does not abut on the secondary transfer unit only at a specific angle position. ,
The secondary transfer apparatus according to claim 3. The secondary transfer device according to any one of claims 3 to 5, wherein the crimp release mechanism and the high-speed decompression mechanism are provided below the secondary transfer unit. The secondary transfer unit has a rotation center and swings,
The secondary transfer device according to any one of claims 3 to 5, wherein the decompression cam is arranged between the rotation center of the secondary transfer unit and the crimp cam. The secondary transfer unit has a rotation center and swings,
The secondary transfer according to any one of claims 3 to 5, wherein the shaft of the separation roller that separates the paper after the secondary transfer from the intermediate transfer belt also serves as the rotation center of the secondary transfer unit. apparatus. The distance between the center of rotation of the secondary transfer unit and the location where the secondary transfer unit receives pressing force from the crimp release mechanism is longer than the distance between the center of rotation of the secondary transfer unit and the secondary transfer roller. The secondary transfer apparatus according to any one of claims 3 to 5, wherein the secondary transfer apparatus is characterized. The secondary transfer device according to any one of claims 1 to 9, wherein the decompression cam comes into contact with a rotating body pivotally supported by the decompression arm. Claims 1 to 10, wherein the crimping arm and the crimping cam are provided at two positions divided into both ends in the axial direction of the secondary transfer roller, and the high-speed decompression mechanism is arranged inside the crimping arm and the crimping cam. The secondary transfer apparatus according to any one. The decompression arms are provided at two positions divided into both ends in the axial direction of the secondary transfer roller, and the decompression arms are connected to each other by a connecting member.
The decompression cam is arranged at the axial center of the secondary transfer roller.
The secondary transfer device according to claim 11, wherein the connecting member abuts on the pressure reducing cam and the pressure reducing arm swings. The decompression arms are provided at two positions divided into both ends in the axial direction of the secondary transfer roller, and the decompression arms are connected to each other by a connecting member.
The decompression cams are arranged near the inside of the crimp cams, respectively.
The secondary transfer device according to claim 11, wherein each decompression cam comes into contact with the connecting member and the decompression arm swings. A feature is that a position detecting means for detecting the angular position of the second driving unit and the decompression cam is arranged inside the two crimping cams provided at both ends in the axial direction of the secondary transfer roller. The secondary transfer apparatus according to claim 11. When the lock mechanism is released, the rotating shaft of the crimping cam can be moved in the axial direction, and the movement releases the engagement between the crimping cam and the abutting member on the crimping arm side.
The secondary transfer device according to any one of claims 1 to 14, characterized in that.